The product, VivaGel, is designed to be inserted into the vagina before sex to help prevent HIV infection. It contains a small protein called a dendrimer that is designed to prevent HIV from attaching to and entering cells.
The protein, SPL-7013, is the first of a number of promising antiviral products developed by Starpharma, a small Melbourne biotechnology company set up in 1996 to commercialise the dendrimer nanotechnology.
“Dendrimer technology allows us to make compounds on the nanometre scale,” Starpharma Development Manager Dr Tom McCarthy told PL. At one nanometre (one thousand-millionth of a metre) to 100 nanometres in size, dendrimers are much larger than the molecules in antiretroviral drugs, a fact which makes them especially suitable for microbicide development.
The SPL-7013 molecule binds to one of HIV’s surface proteins, gp120, to prevent the virus from attaching to and infecting human cells.
In US trials using macaque monkeys, a single application of a gel containing 5 percent SPL-7013 was completely effective in preventing infection with SHIV, an HIV-like virus which infects monkeys. The product was also effective in preventing animal versions of herpes and chlamydia.
The company now plans to begin human tests with a phase I trial, sponsored by the US National Institutes of Health, involving 24 HIV-negative women. The trial, to be run in Adelaide, will examine the gel’s safety for use in humans, looking for any irritation to the vaginal wall or disturbances to the natural bacterial flora of the vagina as well as absorption into the bloodstream. The results of the trial are expected in the second half of 2004.
Worldwide, more than 5000 women are infected with HIV every day. An effective vaginal microbicide has the potential to play a major role in prevention of new infections, especially in the developing world where cultural taboos often prevent women from asking their partners to practice safe sex.
Starpharma believes that the product has considerable potential, both in the developed and developing world. “It’s a protective mechanism that a woman could use when she can’t negotiate the use of a condom,” McCarthy says. “She can apply the gel before sex, with or without the partner knowing and it can offer her a degree of protection.”
